1. Field of the Invention
This invention relates to novel triphenylmethane compounds which are useful as a color former.
2. Description of the Prior Art
Color formers hitherto known include rapid-developing color formers which develop a color rapidly and slow-developing color formers which develop a color slowly when they are adsorbed on acidic substances. Examples of rapid-developing color formers are triarylmethane lactones such as Crystal Violet Lactone, Malachite Green Lactone and 3,3-bis(1',2'-dimethylindol-3'-yl) phthalide, etc., leuco Auramines such as N-bis(4'-dimethylaminophenyl)methylaniline, xanthene lactones such as 3-diethylamino-7-methylaminofluoran, 3-diethylamino-6-chlorofluoran and 3-diethylamino-6-benzylaminofluoran, etc., xanthene lactams such as Rhodamine-N-anilino lactam, indolino-spiropyrans such as 1,3,3-trimethylindolino-.beta.-naphthospiropyran and the like. These rapid-developing color formers are disadvantageous in that they develop a color or are decomposed during storage resulting in a decreased color developing capability and that the colors developed have inferior light-fastness and water-resistance and also changes in the colors diveloped with the lapse of time occur. Examples of slow-developing color formers include Leucomethylene Blue compounds such as N-benzoyl Leucomethylene Blue. Although these color formers have excellent light-fastness, and water-resistance after color formation, they still have disadvantageous in that a color develops upon exposure to light or the compounds are decomposed during storage whereby the color developing capability is decreased.